Cleaning composition



Patented Dec. 6, 1932 UNITED STATES PATENT OFFICE HARRY V. CHURCHILL, OF PARNASS'US, PENNSYLVANIA, ASSIGNOR TO ALUMINUM COMPANY OF AMERICA, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA No Drawing.

This invention relates to the cleaning of aluminum without the use of abrasives and it is particularly concerned with the provision of a water soluble cleaning composition having certain desirable properties in which prior composition provided for this purpose are wholly or in part deficient.

My invention has particular reference to the cleaning of articles such as aluminum ice cube trays of the shape usually used in refrigerating units but my invention is by no means limited to this particular use, the said use merely being a convenient example of such applications in which the cleaning composition is particularly efiicacious, namely, where the stained and discolored aluminum article is of such shape that the ordinary methods of scouring with pumice stone or steel wool would be such a laborious process that the ordinary user of utensils of this nature would resort to strong lye or caustic solutions in order to remove the stain. The use of a strong solution which attacks the aluminum vigorously is not desirable since after several of such cleanings the aluminum article becomes pitted and rough in appearance, and because of the extremely rapid attack, the surface of the utensil presents a spotted and uneven appearance.

The usual methods of cleaning aluminum utensils consist in either scouring the utensil surface with an abrasive combined or uncombined with a cleaning compound, such as a soap, an organic acid, or an alkali, or in boiling the vessel in a solution of an organic acid, for instance, oxalic acid. All of these methods have several apparent drawbacks. The scouring with an abrasivebeing laborious and slow, particularly where the utensil surface is difficult to reach, and the boiling of the utensil in an organic acid, such as a fruit acid, has not been found particularly desirable because of a scum which remains even after the original stain or discoloration has been removed. This scum is dark in appearance and can only be removed by a further scouring operation.

I have discovered that an aqueous solution of an organic fruit acid in which is also contained a small amount of an alkali fluoride CLEANING COMPOSITION Application filed May 18, 1929. Serial No. 364,333.

will, when brought to a temperature somewhat near the boiling point of water, completely remove the stain and discoloration on aluminum articles if the articles are but dipped into the solution for a few moments and then rinsed with hot or warm Water. I have further discovered that it is the presence of the fluoride in the solution. which completely eliminates the objection to the former use of organic fruit acids of this nature, namely, the fluoride appears to remove the resultant scum or general discoloration which is produced by the action of the fruit acid on the metal. The term alkali metal fluorides which describes the alkali salts which may be used for this purpose includes not only sodium and potassium fluorides and bifiuorides, but also ammonium fluoride and other soluble fluorides of a similar nature, and it will be understood that the term alkali metal fluorides, as used herewith and in the claims, describes these particular fluorides as a class. Of them, I have ascertained that sodium fluoride is perhaps the most eflicacious and because of its availability and its form, it is taken as the preferred compound.

The organic fruit acids which may be used in conjunction with the aforesaid fluorides are numerous and comprise malic acid, malonic acid, tartaric acid. citric acid, oxalic acid. and acetic acid. Also in place of these acids, it is possible to use the acid salts such as sodium biacetate and similar salts. In using the term organic fruit acids herewith and in the claims, I mean to comprehend all of the above mentioned and similar acids and acid salts. I have found, in the course of a long investigation concerning the particular benefits of the use of these various organic fruit acids, that certain ones of them are particularly suitable for the cleansing of aluminum. The main desideratum in the cleansing of an aluminum surface is a mild yet steady attack which, when it is completed, leaves a bright apparently unetched surface which does not show any spots or scum due to localized attack of the acid or due to some deposit produced by the acid attack. Therefore, the attack of the acid should not be fast expense of containers such as bottles.

to a quart of water.

-nor should it be violent, the preferred condiobjection that the ox lates are somewhat toxic in nature and their use in a cleaning composition would be objeeted to when the articles to be cleaned are gdbsigned to hold food or other substances for human consumption. Acetic acid and sodium biacetate meet, to a large degree, the requirements of a good cleaner but they are slow in action when used with the fluorides above mentioned and are, as compared with citric or tartaric acids, only 25% eflicient in their cleaning action, it taking approximately about four times as much of the acid salt or the acetic acid to obtain a similar effect. Furthermore, acetic acid is a liquid and therefore has certain disadvantages.

It will be apparent that such a cleaning composition finds its greatest application in ordinary household use and for this purpose it is necessary that the compound be dispensed in a powder form, thus obviating 1jthe or this reason, acetic acid being a liquid is not desirable, it being preferred wherever possible to use a water soluble powder which may be conveniently added in small quantities to Warm water.

In the preferred practice of my invention, I have used a powder consisting of about 1 per cent sodium fluoride, the balance being either citric or tartaric acid, tartaric acid preferably. It has been found that 1 per cent of sodium fluoride produces the most efficient action-although larger or smaller amounts might be conveniently used, particularly if another fluoride of somewhat varied characteristics, such as potassium or ammonium fluoride, were used as a substitute. The powder containing 99 per cent tartaric acid and about 1 per cent of sodium fluoride is mixed in any convenient form and about 5.5 to 6 grams of this material, which would correspond to the usual teaspoonful, is added After the material has been dissolved, the Water is brought to boiling or to a temperature somewhat below boiling and in it is dipped for a period of thirty seconds to two minutes the aluminum utensil from which it is desired to remove the stain or discoloration. At the end of this period, the utensil is removed from the solution and is rinsed in hot water. After this treatment, it will be found that the surface of the utensil is clean, shows no stain or discoloration, and

furthermore, in contrast to the action of the older cleaning solutions, there is no final deposit or scum left on the surface of the utensil. Neither is the aluminum surface pitted or etched to a frosty appearance by the action of the cleaning solution. Instead of dipping the aluminum utensil or other article within the solution, it will, of course, be possible to place the solution within the utensil when it is possible that this may be accomplished. I have found that in general a solution prepared by the use of my novel cleaning composition is most efficient when brought to a temperature sli htly below boiling. However, the liqui may be boiled or a temperature somewhat lower than that preferred may be used. I have preferred, however, to use the temperatures mentioned because of the fact that lower temperatures do not give as rapid and efficient an action.

I claim:

1. A water soluble powder for cleaning aluminum consisting of about 99 per cent of tartaric acid and about 1 per cent of an alkali metal fluoride.

2. A water soluble powder for cleaning aluminum consisting of about 99 per cent of tartaric acid and about 1 per cent of sodium fluoride.

3. A composition for cleaning aluminum consisting of a solid organic fruit acid and a. small amount, at least about 1 per cent, of an alkali metal fluoride.

4. A water-soluble powder for cleaning aluminum comprising organic fruit acid and about 1 per cent of sodium fluoride.

5. A water-soluble powder for cleaning aluminum consisting of organic fruit acid and about 1 per cent of an alkali metal fluoride.

6. A water-soluble powder for cleaning aluminum consisting of about 99 per cent of citric acid and about 1 per cent of alkali metal fluoride.

7. A water-soluble powder for cleaning aluminum consisting of about 99 per cent of citric acid and about 1 per cent of sodium fluoride.

HARRY V. CHURCHILL. 

